Changes in Gene Expression After Exposing Arabidopsis thaliana Plants to Nanosecond High Amplitude Electromagnetic Field Pulses.

The biological effects of exposure to electromagnetic fields due to wireless technologies and connected devices are a subject of particular research interest. Ultrashort high-amplitude electromagnetic field pulses delivered to biological samples using immersed electrodes in a dedicated cuvette have widely demonstrated their effectiveness in triggering several cell responses including increased cytosolic calcium concentration and reactive oxygen species (ROS) production. In contrast, the effects of these pulses are poorly documented when electromagnetic pulses are delivered through an antenna. Here we exposed Arabidopsis thaliana plants to 30,000 pulses (237 kV m-1 , 280 ps rise-time, duration of 500 ps) emitted through a Koshelev antenna and monitored the consequences of electromagnetic fields exposure on the expression levels of several key genes involved in calcium metabolism, signal transduction, ROS, and energy status. We found that this treatment was mostly unable to trigger significant changes in the messenger RNA accumulation of calmodulin, Zinc-Finger protein ZAT12, NADPH oxidase/respiratory burst oxidase homolog (RBOH) isoforms D and F, Catalase (CAT2), glutamate-cystein ligase (GSH1), glutathione synthetase (GSH2), Sucrose non-fermenting-related Kinase 1 (SnRK1) and Target of rapamycin (TOR). In contrast, Ascorbate peroxidases APX-1 and APX-6 were significantly induced 3 h after the exposure. These results suggest that this treatment, although quite strong in amplitude, is mostly ineffective in inducing biological effects at the transcriptional level when delivered by an antenna. © 2023 The Authors. Bioelectromagnetics published by Wiley Periodicals LLC on behalf of Bioelectromagnetics Society.

Mitochondrial DNA haplogroups and variants predispose to chagas disease cardiomyopathy

Cardiomyopathies are major causes of heart failure. Chagas disease (CD) is caused by the parasite Trypanosoma cruzi, and it is endemic in Central and South America. Thirty percent of cases evolve into chronic chagas cardiomyopathy (CCC), which has worse prognosis as compared with other cardiomyopathies. In vivo bioenergetic analysis and ex vivo proteomic analysis of myocardial tissues highlighted worse mitochondrial dysfunction in CCC, and previous studies identified nuclear-encoded mitochondrial gene variants segregating with CCC. Here, we assessed the role of the mitochondrial genome through mtDNA copy number variations and mtDNA haplotyping and sequencing from heart or blood tissues of severe, moderate CCC and asymptomatic/indeterminate Chagas disease as well as healthy controls as an attempt to help decipher mitochondrial-intrinsic genetic involvement in Chagas disease development. We have found that the mtDNA copy number was significantly lower in CCC than in heart tissue from healthy individuals, while blood mtDNA content was similar among asymptomatic Chagas disease, moderate, and severe CCC patients. An MtDNA haplogrouping study has indicated that African haplogroups were over represented in the Chagas subject groups in comparison with healthy Brazilian individuals. The European lineage is associated with protection against cardiomyopathy and the macro haplogroup H is associated with increased risk towards CCC. Using mitochondria DNA sequencing, 84 mtDNA-encoded protein sequence pathogenic variants were associated with CCC. Among them, two variants were associated to left ventricular non-compaction and two to hypertrophic cardiomyopathy. The finding that mitochondrial protein-coding SNPs and mitochondrial haplogroups associate with risk of evolving to CCC is consistent with a key role of mitochondrial DNA in the development of chronic chagas disease cardiomyopathy.

Next-generation sequencing of Tunisian Leigh syndrome patients reveals novel variations: impact for diagnosis and treatment.

Mitochondrial cytopathies, among which the Leigh syndrome (LS), are caused by variants either in the mitochondrial or the nuclear genome, affecting the oxidative phosphorylation process. The aim of the present study consisted in defining the molecular diagnosis of a group of Tunisian patients with LS. Six children, belonging to five Tunisian families, with clinical and imaging presentations suggestive of LS were recruited. Whole mitochondrial DNA and targeted next-generation sequencing of a panel of 281 nuclear genes involved in mitochondrial physiology were performed. Bioinformatic analyses were achieved in order to identify deleterious variations. A single m.10197G>A (p.Ala47Thr) variant was found in the mitochondrial MT-ND3 gene in one patient, while the others were related to autosomal homozygous variants: two c.1412delA (p.Gln471ArgfsTer42) and c.1264A>G (p.Thr422Ala) in SLC19A3, one c.454C>G (p.Pro152Ala) in SLC25A19 and one c.122G>A (p.Gly41Asp) in ETHE1. Our findings demonstrate the usefulness of genomic investigations to improve LS diagnosis in consanguineous populations and further allow for treating the patients harboring variants in SLC19A3 and SLC25A19 that contribute to thiamine transport, by thiamine and biotin supplementation. Considering the Tunisian genetic background, the newly identified variants could be screened in patients with similar clinical presentation in related populations.

Nicotinamide Deficiency in Primary Open-Angle Glaucoma.

Purpose: To investigate the plasma concentration of nicotinamide in primary open-angle glaucoma (POAG). Methods: Plasma of 34 POAG individuals was compared to that of 30 age- and sex-matched controls using a semiquantitative method based on liquid chromatography coupled to high-resolution mass spectrometry. Subsequently, an independent quantitative method, based on liquid chromatography coupled to mass spectrometry, was used to assess nicotinamide concentration in the plasma from the same initial cohort and from a replicative cohort of 20 POAG individuals and 15 controls. Results: Using the semiquantitative method, the plasma nicotinamide concentration was significantly lower in the initial cohort of POAG individuals compared to controls and further confirmed in the same cohort, using the targeted quantitative method, with mean concentrations of 0.14 µM (median: 0.12 µM; range, 0.06-0.28 µM) in the POAG group (-30%; P = 0.022) and 0.19 µM (median: 0.18 µM; range, 0.08-0.47 µM) in the control group. The quantitative dosage also disclosed a significantly lower plasma nicotinamide concentration (-33%; P = 0.011) in the replicative cohort with mean concentrations of 0.14 µM (median: 0.14 µM; range, 0.09-0.25 µM) in the POAG group, and 0.19 µM (median: 0.21 µM; range, 0.09-0.26 µM) in the control group. Conclusions: Glaucoma is associated with lower plasmatic nicotinamide levels, compared to controls, suggesting that nicotinamide supplementation might become a future therapeutic strategy. Further studies are needed, in larger cohorts, to confirm these preliminary findings.

Iron deficiency without anemia is responsible for decreased left ventricular function and reduced mitochondrial complex I activity in a mouse model.

BACKGROUND: Iron deficiency (ID), with or without anemia, is frequent in heart failure patients, and iron supplementation improves patient condition. However, the link between ID (independently of anemia) and cardiac function is poorly understood, but could be explained by an impaired mitochondrial metabolism. Our aim was to explore this hypothesis in a mouse model. METHODS AND RESULTS: We developed a mouse model of ID without anemia, using a blood withdrawal followed by 3-weeks low iron diet. ID was confirmed by low spleen, liver and heart iron contents and the repression of HAMP gene coding for hepcidin. ID was corrected by a single ferric carboxymaltose (FCM) injection (ID + FCM mice). Hemoglobin levels were similar in ID, ID + FCM and control mice. ID mice had impaired physical performances and left ventricular function (echocardiography). Mitochondrial complex I activity of cardiomyocytes was significantly decreased in ID mice, but not complexes II, III and IV activities. ID + FCM mice had improved physical performance, cardiac function and complex I activity compared to ID mice. Using BN-PAGE, we did not observe complex I disassembly, but a reduced quantity of the whole enzyme complex I in ID mice, that was restored in ID + FCM mice. CONCLUSIONS: ID, independently of anemia, is responsible for a decreased left ventricular function, through a reduction in mitochondrial complex I activity, probably secondary to a decrease in complex I quantity. These abnormalities are reversed after iron treatment, and may explain, at least in part, the benefit of iron supplementation in heart failure patients with ID.

Resveratrol Directly Binds to Mitochondrial Complex I and Increases Oxidative Stress in Brain Mitochondria of Aged Mice.

Resveratrol is often described as a promising therapeutic molecule for numerous diseases, especially in metabolic and neurodegenerative disorders. While the mechanism of action is still debated, an increasing literature reports that resveratrol regulates the mitochondrial respiratory chain function. In a recent study we have identified mitochondrial complex I as a direct target of this molecule. Nevertheless, the mechanisms and consequences of such an interaction still require further investigation. In this study, we identified in silico by docking study a binding site for resveratrol at the nucleotide pocket of complex I. In vitro, using solubilized complex I, we demonstrated a competition between NAD+ and resveratrol. At low doses (<5µM), resveratrol stimulated complex I activity, whereas at high dose (50 µM) it rather decreased it. In vivo, in brain mitochondria from resveratrol treated young mice, we showed that complex I activity was increased, whereas the respiration rate was not improved. Moreover, in old mice with low antioxidant defenses, we demonstrated that complex I activation by resveratrol led to oxidative stress. These results bring new insights into the mechanism of action of resveratrol on mitochondria and highlight the importance of the balance between pro- and antioxidant effects of resveratrol depending on its dose and age. These parameters should be taken into account when clinical trials using resveratrol or analogues have to be designed.

Bioenergetic defect associated with mKATP channel opening in a mouse model carrying a mitofusin 2 mutation.

Charcot-Marie-Tooth disease type 2A (CMT2A) is an autosomal dominant axonal form of peripheral neuropathy caused by mutations in the mitofusin 2 gene (MFN2), which encodes a mitochondrial outer membrane protein that promotes mitochondrial fusion. Emerging evidence also points to a role of MFN2 in the regulation of mitochondrial metabolism. To examine whether mitochondrial dysfunction is a feature of CMT2A, we used a transgenic mouse model expressing in neurons a mutated R94Q form of human MFN2 shown to induce a CMT2A phenotype. Oxygraphic and enzymatic measurements both revealed a combined defect of mitochondrial complexes II and V (40 and 30% decrease, respectively) in the brain of Tg-R94 mice, leading to a drastic decrease of ATP synthesis. These deficiencies were reversed by the mitochondrial ATP-sensitive potassium channel (mK(ATP)) inhibitor 5-hydroxydecanoate. Conversely, in controls and wild-type human MFN2 mice, the mK(ATP) activator diazoxide mimicked the deficiency observed with the R94Q mutation. The physical links between complexes II and V, previously proposed as part of mK(ATP), were reinforced in Tg-R94Q mice. Our results show that the R94Q MFN2 mutation induces a combined defect of complexes II and V linked to the opening of mK(ATP), which could participate in the pathophysiology of the disease.